1. Field of the Invention
The present invention relates to a method and apparatus for reducing a patient's fractured bone using an elongated bone plate that has a plurality of openings therethrough, the openings having countersunk portions that correspond in shape to the countersunk head portion of a bone screw used to affix the bone plate to the patient's tissue and improved provisional fixation pins that preliminarily affix the plate in a selected position. Even more particularly, the present invention relates to an improved method and apparatus for reducing a patient's fractured bone at a fracture site wherein provisional fixation pins are used to preliminarily position the bone plate prior to permanent attachment with bone screws, each provisional fixation pin featuring a lower drilling tip portion and an enlarged diameter middle section having a surface that fits the countersunk openings of the bone plate. The lower drilling tip portion is smaller in diameter than the final bone screws to be used for permanent affixation.
2. General Background of the Invention
Bone plates have long been used to reduce and stabilize a patient's fractured bone at a fracture site. Bone plates are often shaped to conform to the patient's bone, having a concave rear surface shaped to fit a long bone of the leg or arm. Presently, many bone plates provide openings that include countersunk surfaces that are sized and shaped to conform to the countersunk head bone screws used to attach the bone plate to the patient's bone tissue.
One of the problems with the placement of a bone plate during surgery is that the bone screws used in cooperation with the plate typically have a diameter and distal tip that are imprecise when trying to perfectly place the screw. Often times, the surgeon misplaces a bone screw by a millimeter or two so that the plate is misaligned when all of the bone screws are finally implanted through the bone plate and into the patient's underlying bone tissue. This problem of preliminary fixation of bone plates has been recognized in the art.
Bone clamps are the standard method of provisionally attaching a plate to the bone prior to placing the bone screws through the plate. At least one spinal cervical plate for use in vertebral interbody fusions provides series of smaller holes in addition to the larger screw holes. These smaller holes accept pins that temporarily position the plate prior to placement of the larger bone screws. Clamps are not practical in the cervical area of the body. The limitations of these pins, however, is that they have no threads and must be driven in. This dictates that such pins can only be used to position the plate and not to hold the fracture reduced (i.e., hold the bone to the plate along the axis of the pin). In the case of a comminuted fracture with small bone fragments, attempting to drive the pins in instead of screwing them in may further displace the fragment from the plate.
There has been some discussion of standard bone plates with smaller holes similar to those in the spinal plates. These holes are used with standard K-Wires that have no shoulder and only position the plate, not affix it to the bone. Another draw back to this prior art methods is that it requires a special corresponding plate with small holes to accommodate the pins and cannot be used with standard bone plates.
One patent that discusses fixation pins for small bone fragments is the Pennig Pat. No. 5,433,719, entitled "Fixation Pin For Small-Bone Fragments". The '719 patent contemplates an implantable fixation pin for retaining small bone fragments in an osteosynthesis procedure. The pin comprises a smooth-walled shank portion and an adjoining threaded portion, wherein a step-down conical shoulder is formed between the shank portion and the threaded portion.
The Hausman Pat. No. 5,676,667 discloses a fixation plate for fixing the position of a fractured bone. The plate includes an elongated rigid plate having a plurality of first aperture spaced along the length of the plate. The first apertures are arranged and sized to receive threaded fasteners for fastening the plate to the bone on both sides of the fracture. The fixation plate also includes a plurality of second apertures spaced along the length of the plate. The second apertures, which are smaller than the first apertures, are arranged and sized to receive tacks to temporarily attach the plate to the bone on both sides of the fracture.
A publication that discusses the reduction of bone using plates and illustrates bone clamps is the Smith & Nephew Orthopaedics Information Catalog entitled "Aline.TM. Anterior Cervical Plating System".